Going Nuclear: Before and After

Ever a 'threat,' never an atomic power, Iran points up challenges of nuclear technology By CHARLES HANLEY

[AP] Feb. 27, 2007 The Iranians may have an atom bomb within two years, the authoritative Jane's Defence Weekly warned. That was in 1984, two decades ago.

Four years later, the world was again put on notice, this time by Iraq, that Tehran was at the nuclear threshold, and in 1992 the CIA foresaw atomic arms in Iranian hands by 2000. Then U.S. officials pushed that back to 2003. And in 1997 the Israelis confidently predicted a new date -- 2005.

Now, as 2006 wears on, and a global focus sharpens on Iran's nuclear ambitions, the coming of any Iranian doomsday arsenal looks to be years away, experts say. Those past predictions consistently underplayed the technological challenges of a bomb program.

Iran itself, which said Tuesday it has begun enriching small amounts of uranium, denies its enrichment program is intended to produce anything beyond weaker fuel for civilian nuclear power plants, not the highly enriched uranium that can fuel a bomb.

The United Nations Security Council is expected to take up the issue next month, when skeptics may push for sanctions against Tehran. But few specialists view a potential Iranian bomb as an imminent threat.

In fact, the latest estimate from the CIA and other U.S. intelligence agencies sees no Iranian bomb before the next decade. Israeli defense experts agree, speaking of a 2012 date.

"It's a very complicated process requiring precision from design and engineering to manufacture and installation, and there's a lot of room for problems," said Hinderstein, who for a decade has tracked Iranian nuclear developments with the Institute for Science and International Security.

Enrichment occurs in vast arrays of centrifuges, thin-walled cylinders of strong but superlight materials -- typically three to six feet tall and several centimeters wide -- into which uranium gas is fed. Each of these "rotors," with just a few milligrams of gas, spins on its axis at up to 70,000 revolutions per minute, separating the heavier uranium-238 from the rarer U-235, the isotope whose nucleus can "fission" to produce energy.

Pumped through thousands of "cascading" cylinders, the mixture's content is gradually boosted to over three per cent U-235, the level needed for power generators. If extended, the process can produce 90 per cent enriched uranium, the stuff of bombs.

"A vast percentage of centrifuges have to be rejected in testing, up to 60 percent rejection," said Frank Barnaby, a former British weapons scientist, now with the Oxford Research Group.

The Iranians plan to install 50,000 centrifuges in huge underground halls at Natanz, Iran. But fewer than half the 1,140 machines they had assembled by 2004, using ultrathin aluminum, were good enough to use in cascades, the UN nuclear agency has reported. And problems develop not only with materials, said a retired U.S. centrifuge specialist.

"There are also problems with scoops and other things on the inside. You have to design the electronics that give you variable frequencies. You have to lubricate them properly, hook them together properly, maintain the vacuum," said this scientist, speaking on condition he not be named because of his sensitive former government position.

Hinderstein's ISIS calculates that at its last known assembly rate of about 100 per month, Iran would take years to emplace thousands of centrifuges at Natanz, a plant that theoretically could eventually produce highly enriched uranium for dozens of bombs a year.

The ISIS experts suggest Iran could speed things up with a basic small plant of 1,500 centrifuges, to produce enough bomb fuel for one weapon. Even then, the assembly, testing and production process would take the project into 2009, they estimate.

And, asked Barnaby, "who do you deter with just one weapon?"

Even before the centrifuge stage, however, Iran must overcome another technical problem.

Too many impurities remain in the gas produced from processed uranium ore, or yellowcake, at Iran's uranium conversion facility, the magazine Science reported last month, quoting an unidentified U.S. government official.

The gas conversion facility was built on a Chinese design, but Beijing backed out of the project in 1998, leaving the Iranians without Chinese expertise to ensure the best product.

Contaminants in the uranium hexafluoride gas can block valves and piping. "Those impurities do muck up your centrifuges," Barnaby said. "It's not a problem if you want 3.5 per cent enriched uranium for power plants, but if you go to 90 percent these impurities are a major problem."

Few specialists doubt that the Iranians, with years of work, could overcome such engineering problems. But are they seeking a bomb?

Mustafa Kibaroglu, of Ankara's Bilkent University, told The Associated Press nine years ago that Iran was incapable of building a nuclear weapon earlier than 2012. Now that his is a widely accepted timetable, this Turkish expert, who has consulted with Iranian leaders, says politics, more than technology, will be the deciding factor.

"Having the capability to build weapons doesn't mean that they will build nuclear weapons," he said. "This is an issue yet to be decided by Iran's (Muslim) clerical leadership. This issue is not to be discounted."